cmd/goimports: update doc, remove old gofmt flags

Don't say the word "fork" (not accurate), and remove the
tab/comment flags that were removed from gofmt.

LGTM=adg
R=golang-codereviews, adg
CC=golang-codereviews
https://golang.org/cl/61410052

cmd/goimports/doc.go

@@ -5,13 +5,12 @@ adding missing ones and removing unreferenced ones.
 
      $ go get code.google.com/p/go.tools/cmd/goimports
 
-It's a fork of gofmt, and will also format your code, so it can be
-used as a replacement for your gofmt-on-save hook in your editor of
-choice.
+It's a drop-in replacement for your editor's gofmt-on-save hook.
+It has the the same command-line interface as gofmt and formats
+your code in the same way.
 
-For emacs, make sure you have the latest (Go 1.2) go-mode.el:
+For emacs, make sure you have the latest (Go 1.2+) go-mode.el:
    https://go.googlecode.com/hg/misc/emacs/go-mode.el
-
 Then in your .emacs file:
    (setq gofmt-command "goimports")
    (add-to-list 'load-path "/home/you/goroot/misc/emacs/")
@@ -19,7 +18,6 @@ Then in your .emacs file:
    (add-hook 'before-save-hook 'gofmt-before-save)
 
 For vim, set "gofmt_command" to "goimports":
-
     https://code.google.com/p/go/source/detail?r=39c724dd7f252
     https://code.google.com/p/go/source/browse#hg%2Fmisc%2Fvim
     etc

cmd/goimports/goimports.go

@@ -26,15 +26,16 @@ var (
 	write  = flag.Bool("w", false, "write result to (source) file instead of stdout")
 	doDiff = flag.Bool("d", false, "display diffs instead of rewriting files")
 
-	options  = &imports.Options{}
+	options = &imports.Options{
+		TabWidth:  8,
+		TabIndent: true,
+		Comments:  true,
+	}
 	exitCode = 0
 )
 
 func init() {
 	flag.BoolVar(&options.AllErrors, "e", false, "report all errors (not just the first 10 on different lines)")
-	flag.BoolVar(&options.Comments, "comments", true, "print comments")
-	flag.IntVar(&options.TabWidth, "tabwidth", 8, "tab width")
-	flag.BoolVar(&options.TabIndent, "tabs", true, "indent with tabs")
 }
 
 func report(err error) {